The main purpose of this proposal is to determine the independent effects of gender and adiposity on fat metabolism during the major physiologica lconditions which decrease lipolysis and fat oxidation (hyperinsulinemia) or increase the mobilization and use of fat as a fuel (fasting and endurance exercise). We hypothesize that differences in fat metabolims between men and women will become more apparent during the physiological challenges of hyperinsulinemia, exercise, and fasting.